Public access defibrillator

ABSTRACT

A publically available external defibrillator includes a detector used to detect a life threatening condition of a patient, a controller operating the defibrillator automatically and a therapy delivery circuit that delivers appropriate therapy. The defibrillator is attached to a patient by any attendant or bystander and once it is attached, the defibrillator is adapted to monitor the patient and when a life threatening condition is detected, to apply therapy automatically, i.e., without any involvement by the patient or the attendant.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention pertains to an external defibrillator adapted to providetherapy selectively to patients suffering from sudden acute cardiacarrest. More particularly, the present invention pertains to an externaldefibrillator which is constructed and arranged to operate substantiallyautomatically once it is positioned on the patient. The defibrillatorrapidly determines the status of the patient, makes a decision onwhether therapy is indicated, and, if necessary, applies such therapyuntil either its operation is discontinued externally or sinus rhythmhas been achieved.

DESCRIPTION OF THE PRIOR ART

The term Sudden Cardiac Arrest or SCA in a patient refers to a conditioncharacterized by a loss of effective pumping action in the heart and isgenerally caused by an arrhythmia. SCA results in an abrupt cessation ofblood circulation to the vital organs, and once it occurs, unless thepatient's heart is reverted rapidly to a sinus rhythm, death will occur.In fact SCA is considered to be the leading cause of death in the UnitedStates and throughout the world.

Arrhythmias which cause SCA include ventricular tachycardia andventricular fibrillation. Ventricular tachycardia is characterized byelectrical disturbances which cause a dangerously high cardiac rate andmay lead to ventricular fibrillation. Ventricular fibrillation refers toa state where cardiac electrical activity is completely disorganized andthe heart is quivering. During ventricular fibrillation, the heart doesnot pump blood, and no beats can be detected.

Arrhythmias may be detected from the patient's electrocardiogram (ECG),blood pressure, blood oxygenation level and other similar physiologicalparameters. Because the signals indicative of these parameters can bevery complex, various algorithms are used to analyze these parameters todetect and classify an arrhythmia. Once detected, the arrhythmia can beeliminated by using antitachycardia therapy consisting of electricalstimulation. Two kinds of devices are presently available to provideantitachyarrhythmia therapy: internal or implanted cardioverterdefibrillators (ICDs), and external defibrillators.

ICDs have been known since the early 1980s. These devices are implantedin the patient and include electrodes extending to the cardiac chambersto sense intrinsic cardiac activity and to provide stimulation signals.The intrinsic signals sensed in the cardiac chambers are used toclassify the condition of the heart, and if a tachyarrhythmia isdetected, then either cardioversion pacing pulses or defibrillationshocks are applied.

In order for these kinds of devices to function properly, a clinicianexamines the patient and, after implantation, programs a plurality ofparameters into the ICD which are used by a processor to classify thecondition of the patient and determine the characteristics of thestimulation signals to be applied. Frequently these parameters areselelected after the patient's heart rate is increased either naturally,with exercise, or with drugs. It is advisable to re-program theseparameters as the condition of the patient changes over time.

External defibrillators capable of providing defibrillation shocks orother types of therapy are also well known. Current externaldefibrillators must be operated manually by a trained professional suchas an emergency medical technician, paramedic, firefighter, or policeofficer, etc. Existing external defibrillators do not monitor cardiacactivity before a sudden cardiac arrest episode, and accordingly, theprofessional must examine the patient and determine his condition first,before any therapy is provided. Hence, inherently, the existing externaldefibrillators cannot be used by a layperson.

An external defibrillator described in commonly assigned U.S. Pat. No.5,474,574 and incorporated herein by reference includes an ECG sensorand requires several parameters to be programmed by a clinician beforeit can be used properly. Some of the programmable parameters pertain tothe sensitivity of the ECG sensor required to detect ECGs reliably.Other parameters pertain to the size, number and duration of the shocksto be applied by the device. Since these parameters must be programmedseparately for each patient, by the time this defibrillator is ready tobe used, it is configured to a specific patient and cannot be used for adifferent patient without first reprogramming its parameters.

In summary, existing external defibrillators are limited in that theymust be operated by a professional, they do not have the capability tocontinuously monitor a patient; and they require active intervention toinitiate any therapy.

There is a need for an automatic external defibrillator which can beused successfully by a layman, i.e., a person without any formal medicaltraining.

BRIEF SUMMARY OF THE INVENTION

In view of the above, an objective of the present invention is toprovide an external defibrillator which can be distributed and placed atpublic places which can be used effectively by a person with no specialmedical training.

A further objective is to provide an external defibrillator able tomonitor a patient and determine automatically if a patient is in need oftherapy.

A further objective is to provide an external defibrillator capable ofproviding cardiac therapy without requiring any information about thepatient receiving it.

Yet another objective is to provide an external defibrillator which hasseveral modes of operation so that it can be used for differentpurposes.

Other objectives and advantages of the invention will become apparentfrom the following description.

Briefly, an external defibrillator constructed in accordance with thisinvention includes a sensing circuit used to sense physiological signalsindicative of cardiac activity, a therapy delivery circuit thatgenerates pacing or shock pulses, and a controller that is used tooperate the defibrillator automatically. Signals indicative of intrinsiccardiac activity, including R-waves and ventricular fibrillation, forexample, are determined using generic criteria rather thanpatient-specific programming parameters. Similarly, the pulses appliedto the patient to effect therapy have characteristics which are derivedfrom general statistical data and are not patient specific. Thedefibrillator recognizes a life threatening cardiac condition and canapply appropriate therapy without any human input or intervention.

Optionally, the external defibrillator may include a memory for loggingdata for each episode during which therapy is applied. A display mayalso be provided to show instructions for the operation of thedefibrillator and/or to selectively display the logged data. Acommunication module may also be provided to contact remote locationsand obtain assistance for the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an external defibrillator constructed inaccordance with this invention;

FIG. 2 shows a flow chart for the operation of the defibrillator of FIG.1;

FIG. 3 shows a block diagram of the sense and the therapy deliverycircuits of FIG. 1; and

FIG. 4 shows a block diagram of the arrhythmia detector of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIG. 1, an external defibrillator 10 constructed inaccordance with this invention may include several subsystems asdescribed below, it being understood that not all the subsystems arenecessary for the system to operate. Generally speaking, thedefibrillator 10 is coupled to patient 11 by electrodes strategicallyplaced on the patient's body to permit the defibrillator 10 to collectinformation from the patient regarding his current status and to delivertherapy. For the sake of simplicity, FIG. 1 shows symbolically twoelectrodes 12 and 14 being used to detect signals indicative of thecardiac condition of the patient and to deliver therapy, respectively,it being understood that more electrodes may be required to performthese functions, and that some electrodes may be used for both thesefunctions.

The signals acquired by electrode 12 are received by a sense circuit 18which analyzes these signals and determines various cardiac parameters,such as the current cardiac rhythm. This information is fed to thecontroller 20. The controller, a microprocessor, uses the parametersreceived from the sense circuit 18 together with other information todetermine the current condition of the patient. For this purpose thecontroller 20 provides the parameters to an arrhythmia detector 22. Forthe sake of clarity, this detector is shown in FIG. 1 as a separatesubsystem, but preferably it is implemented as software within thecontroller 20. Once the controller determines that therapy is required,it activates a therapy delivery circuit 24 which then delivers suitableshocks or other electrical signals through electrode 14.

Information obtained from or about the patient, as well as dataregarding therapy applied to the patient, is logged by a data loggingcircuit 28. Some of this information may be downloaded to a printer orshown on a display if so desired.

Power to the defibrillator is provided by a power supply 30 which mayinclude rechargeable or replaceable batteries.

A self-test and diagnostic circuit 32 is used to monitor the othersubsystems of the defibrillator as described below. For example, thecircuit 32 may monitor the power supply 30. If it determines that thepower supply has a low energy backup capability, it may disable thetherapy delivery circuit but allow continued monitoring of the patient.If the power supply level is very low, the circuit 32 may shut down thewhole defibrillator.

Circuit 32 may also monitor the coupling between the electrodes and thecorresponding organ tissues. For example, circuit 32 may determine theimpedance between the two electrodes. If this impedance is too high, thedefibrillator may be inhibited from operating.

Circuit 32 may also include a watchdog circuit (not shown) which isadapted to receive a signal from the controller 20 at predeterminedintervals. In the absence of these signals, the watchdog circuit 32determines that the controller 20 is inoperative and may shut down thedefibrillator. The other elements and subsystems of the defibrillator 10may be monitored by the circuit 32 in the same manner.

A communication module 34 is used to establish communication with theoutside world and to provide information to a remote device about thecurrent operation and status of the defibrillator 10. For example, thecommunication module 34 may include a cellular telephone capable ofaccessing an emergency number associated with a police station or anemergency room. Preferably, the communication module 34 also includes ameans of identifying the location of the defibrillator 10 to the remotedevice. This means may include a Global Positioning System (GPS) orother geographic locating systems.

The operation of the defibrillator is now discussed in conjunction withthe flow chart of FIG. 2. While other modes of operation are alsopossible, preferably the defibrillator 10 operates in a completelyautomatic mode in which, once it is attached to the patient, does notrequire any intervention from the patient or an attendant. Therefore,the defibrillator can be used by virtually anyone, with no trainingrequired. For the purposes of this flow chart in the following scenarioit is assumed that a patient has suffered a sudden cardiac arrest. Apasserby notices that the patient is in distress and that an automaticdefibrillator is nearby. The passerby attaches the electrodes of thedefibrillator to the chest of the patient in accordance withinstructions on the defibrillator, and he then activates a switch 36indicating that the defibrillator 10 is properly in place. Theactivation of switch 36 awakens the controller 20 (step 202).

In step 204 the self-test/diagnostic circuit 32 (FIG. 1) is activated.The circuit 32 checks the power reserves of power supply 30, theimpedance between the electrodes 12 and 14, and any other criticalportions of the system that may require attention. If during thisself-check an abnormal condition is detected, an error indication isgenerated and the operation of the defibrillator 10 is halted. Forexample, if the impedance between the electrodes is too high, a messagemay be generated requesting that the electrodes be repositioned.Similarly, if the power supply voltage is determined to be too low, thena message may be generated indicating that new batteries are required.These messages may be shown in the display 38 (FIG. 1). Additionally, oralternatively, an audio signal may be activated whenever the self-testindicates a problem with the system. The self test and diagnosticcircuit 32 (FIG. 1) may operate at regular intervals once thedefibrillator is activated.

If the self-test step 204 indicates that the defibrillator isoperational, then in step 206 the sense circuit 18 is activated todetermine the current cardiac activity . As mentioned above, there aremany physiological signals that can be used to perform this function,such as the ECG, blood pressure, pulse oximetry, and so on. In thepresent description, it is assumed that the ECG is analyzed. As shown inFIG. 3, two electrodes 12A and 12B are used to measure the ECG Theseelectrodes are attached across the chest of the patient in a well-knownmanner. The two electrodes 12A, 12B are connected to a protectioncircuit 40. The purpose of the protection circuit 40 is to isolate thedefibrillator 10 electrically from the patient and other sources ofelectrical signals. The signals from the electrodes 12A, 12B passthrough the protection circuit 40 and then are amplified by an amplifierstage 42. After amplification, the signals pass through a filter stage44 which eliminates noise from the signals. The filtered signals arenext fed to a comparator stage 46 which insures that the signals fallwithin a predetermined range. The resulting signals are then sent to thecontroller 20 and arrhythmia detector 22.

Referring now to FIG. 4, the arrhythmia detector 22 includes a QRSdetector 60 adapted to detect a QRS complex. Since the defibrillator 10has no information specific to the patient, the QRS detector must usegeneric criteria for detecting the QRS complexes, based, for example, onstatistical information collected from other patients. Once a QRScomplex is detected, a signal is sent to an R—R interval calculator 62which uses the QRS complexes to calculate successive R—R intervals. Thecurrent R—R interval is provided to a comparator 64 which uses certaingeneric criteria to determine if the patient is suffering fromventricular tachycardia.

A combination of heart rate and morphology analysis is used to detectventricular tachycardia. A rhythm is classified as ventriculartachycardia when the heart rate is higher than ventricular tachycardiadetection rate but lower than ventricular fibrillation detection rateand the morphological analysis indicate wide QRS complex.

Once ventricular tachycardia is detected, its rate is determined by ratedetector 68 and this rate is provided to the controller 20.

In addition, the detector 22 may also include a ventricular fibrillationdetector 66 which analyzes the ECG signals from sense circuit 18 todetect ventricular fibrillation.

Ventricular fibrillation is detected when the heart rate excesses theventricular fibrillation rate or when the heart rate is irregular andthe rhythm is proceeded by a shockable rhythm, which can be eitherventricular tachycardia or ventricular fibrillation.

Other analysis methods for signal processing can be used for detectinglife threatening arrhythmias, for examples, R—R interval variability,amplitude variability, amplitude distribution analysis, probabilitydensity function, template matching, on-set analysis, signed or unsignedarea under the curve, waveform factor, complexity analysis, modulardomain function, frequency domain analysis, Q-T interval analysis, andS-T analysis.

Returning to FIG. 2, in step 206 the sense circuit 18 detects intrinsiccardiac signals, as discussed above. In step 208 these signals areanalyzed by the QRS detector. If a QRS complex is detected, in step 210the R—R interval calculator and comparator 64 (FIG. 4) determineswhether life-threatening ventricular tachycardia (VT) is present. If instep 210 VT is not detected then it tests to see if the amplitude isless than a threshold, e.g. 0.2 millivolts. If the amplitude is lessthan the threshold, the rhythm is classified as fine ventricularfibrillation if it is proceeded by a shockable rhythm and the rhythm isclassified as asystole if it is proceeded by a nonshockable rhythm.

If in step 210 VT is detected, and if controller 20 is equipped with acommunication module 34, then in step 212 the controller 20 activatesthe communication module 30 to send a message to a service center, e.g.a police station and/or an emergency room that an emergency conditionexists and that the defibrillator 10 is preparing to applyanti-tachycardia therapy.

FIG. 3 also shows details of the therapy delivery circuit 24. Thecircuit 24 includes a low-voltage pulse generator 50 receiving commandsfrom controller 20 and generating antitachycardia pacing pulses. Thesepulses are fed through a protection circuit 52 to a pair of outputelectrodes 14A, 14B. The protection circuit 52 is used to isolate thecircuit 24 from the patient.

Therapy circuit 24 further includes a high voltage shock generator 54,with or without a charge dump resistor 56 and an electronic switch 58.The generator 54 and switch 58 are responsive to commands fromcontroller 20. When the high voltage shock generator 54 receives acommand from the controller 20 indicating that a shock may be required,the generator charges an internal capacitor (70) to a predeterminedvoltage. This capacitor 70 can be selectively discharged either toelectrodes 14A, 14B or to a charge dissipating resistor 56 by switch 58depending on the commands issued by controller 20.

Referring back to FIG. 2, in step 214, the controller 20 generates acommand to apply antitachycardia therapies, e.g. pacing pulses orcardioversion shocks. In response, the generator 50 generatesantitachycardia therapies to the electrodes 14A, 14B. Preferably theseantitachycardia therapies are generated and applied synchronously withthe detected QRS complexes. More particularly, each pacing pulse orcardioversion shock may be applied within a specified time, e.g. 60milliseconds after a QRS complex (or R-wave) to insure that the therapyis not applied during a T-wave. This type of synchronized ventriculartachycardia therapy is important because it has been found that atherapy delivered on a T-wave can induce ventricular fibrillation, acondition worse than ventricular tachycardia. In some prior-art externaldefibrillators, a manual synchronizing button was provided. The presentdefibrillator is superior to these prior art defibrillators because itsynchronizes automatically antitachycardia therapy, either pacing orcardioversion, to the R-waves, thereby advantageously reducing thechances of inducing ventricular fibrillation. This mode is furtheradvantageous because it reduces the delay in applying therapy to thepatient and it eliminates possible operator error.

If in step 208 a QRS complex is not detected, then in step 214 theventricular fibrillation detector 66 (FIG. 4) and rate detector 68 areused to detect a life threatening ventricular fibrillation. In thepresence of this condition, in step 218 a message is sent indicatingthat defibrillation shock therapy is required.

In step 220, the controller 20 (FIG. 1) sends a command to the highvoltage shock generator 54 (FIG. 3) to set the HV generator and to causeit to charge its capacitor 70. In step 222 a reconfirmation step isprovided. In this step a final decision is made as to whether ahigh-level defibrillation shock is required. One criteria for thisdetermination may be to check the output of rate detector 68 (FIG. 4) todetermine if a life threatening ventricular fibrillation is stillpresent. Another criterion could be to check whether switch 36 (FIG. 1)has been activated. This switch 36 now may be activated, for example, bythe patient, if conscious, or by the attendant in the case that thedefibrillation shock is not required. If in step 222 it is determinedthat a fibrillation shock is not necessary, then in step 224 the energyof internal capacitor 70 is dumped by switch 58 through resistor 56(FIG. 3). Otherwise, in step 226 a shock is applied through theprotective network 52 (FIG. 3) and electrodes 14A, 14B, to the patient.A cardioversion or defibrillation shock can be either mono-phasic ormulti-phasic. Again, the parameters for the cardioversion anddefibrillation shocks can be generic or can be patient specific.Preferably each therapy is delivered synchronously with the cardiacfibrillations if possible.

In another embodiment, the detection circuit can have only oneindicative signal for all life threatening arrhythmias, which includeventricular tachycardia and ventricular fibrillation. A therapy isdelivered to the patient as either synchronized cardioversion to an Rwave or asynchronized defibrillation if no R waves are found.

In FIGS. 1, 3 and 4, separate electrodes 12, 14 or correspondingelectrode pairs 12A, 12B and 14A, 14B of the sensing circuit 18 ortherapy delivery circuit 24 are shown as being used to acquire signalsfrom the heart and to deliver therapy. However, a single pair or set ofelectrodes may be used to perform both functions.

Once the controller 20 becomes active and the defibrillator 10 haspassed the self-test step 204, its operation is automatically logged inthe data log memory 28. The logging includes details of the QRScomplexes sensed, the ventricular tachycardia or fibrillation rates, anda history of the therapy applied to a patient. This information may beselectively uploaded from data log memory 28 to a separate location. Inaddition, the defibrillator 10 may be provided with the display 38 whichmay be used to provide instructions for the operation of thedefibrillator 10 or to display the data logged in memory 28. The memory28 may include a hard disk, an optical disk, a solid state memory, aflash card, a CD recorder or a combination of any of these devices.

In summary, an external defibrillator is described herein which canprovide automatic therapy to patients with life threatening arrhythmiasor sudden cardiac arrest. Any person can attach the device to thepatient since no special training is required. Once the defibrillator isproperly attached to the patient, the condition of the patient iscontinuously and automatically monitored. The defibrillator analyzesphysiological signals of the patient to automatically detect anarrhythmia and deliver therapy to the patient if necessary, usinggeneric criteria. An important feature of the invention is that it isbased on a programmable controller whose programming parameters are notcustomized for each patient, but instead contain generic parameterswhich allow the defibrillator to operate effectively for any patient.Consequently, the defibrillator can be effective without reprogrammingbetween patients.

Although the main operation mode is fully automatic, different operationmodes, such as advisory or manual, can be included to provide a trainedoperator the control to the device.

The defibrillator performs a self-test to insure that all itscomponents/subassemblies and the connections to the patient areoperational. When the self-test and diagnostic circuit detects amalfunction, a visual indication and/or an audio signal can indicatethat the defibrillator is not operational.

The defibrillator may be provided with a display for showinginstructions, error messages, data descriptive of the patient'scurrent/past condition, and the therapy applied by the defibrillator.

A communication module may be also be provided within the defibrillatorto alert personnel at a remote location that the patient has experienceda life threatening episode and that therapy is being delivered by theautomatic defibrillator. Emergency personnel (such as an ambulance) maybe dispatched to provide assistance. Data from the data logging memorymay also be transmitted at the same time. The communication module mayinclude a locator unit such as a GPS (Global Positioning System) whichcan provide the physical location of the patient. The communicationmodule may make use of a cellular telephone system, wireless radio ortelephone system, a controller network, the Internet, and so on. Thecommunication module may also be activated by the self-test anddiagnostic circuit if tests show that the defibrillator needs servicingor repair.

The sensing of physiological signals and therapy can be affected ondifferent electrodes dedicated for each of these functions, or can beaffected on a single set of electrodes.

Obviously, numerous modifications may be made to this invention withoutdeparting from its scope as defined in the appended claims.

We claim:
 1. An external defibrillator that can be used to apply therapyto any patient, comprising: an electrode adapted to couple externally tothe body of a patient; a sense circuit coupled to said electrode tosense a physiological signal of the patient indicative of intrinsiccardiac activity; a cardiac arrhythmia detector coupled to said sensecircuit to detect a life threatening cardiac arrhythmia based on saidphysiological signal; a microprocessor-based controller adapted togenerate automatically a command in the presence of said cardiacarrhythmia; and a therapy delivery circuit adapted to deliver electricaltherapy pulses to said patient to correct said cardiac arrhythmia inresponse to said command, and a comparator adapted to compare saidphysiological signal to a threshold value, said threshold value beinggeneric to cardiac patients.
 2. An external defibrillator that can beused to apply therapy to any patient, comprising: an electrode adaptedto couple externally to the body of a patient; a sense circuit coupledto said electrode to sense a physiological signal of the patientindicative of intrinsic cardiac activity; a cardiac arrhythmia detectorcoupled to said sense circuit to detect a life threatening cardiacarrhythmia based on said physiological signal a microprocessor-basedcontroller adapted to generate automatically a command in the presenceof said cardiac arrhythmia; a therapy delivery circuit adapted todeliver electrical therapy pulses to said patient to correct saidcardiac arrhythmia in response to said command, and wherein said sensecircuit includes a signal detector adapted to detect a specific cardiacsignal based on generic criteria.
 3. A publicly accessible externaldefibrillator for automatically generating a generic cardiac therapy fora person suffering from a life threatening cardiac condition, saidexternal defibrillator comprising: a first electrode adapted to beattached to said patient; a detector circuit coupled to said firstelectrode and adapted to detect a life threatening cardiac conditionbased on a physiological signal sensed through said electrode, saiddetector circuit detecting said cardiac condition using non-patientspecific criteria; a microprocessor-based controller coupled to saiddetector circuit and adapted to generate a command in the presence ofsaid life threatening condition; and a pulse generator adapted togenerate therapeutic pulses selected to a pulse generator adapted togenerate therapeutic pulses selected to terminate said life threateningcardiac condition in response to said command.
 4. The externaldefibrillator of claim 3 further comprising a second electrode attachedto said patient and being coupled to said pulse generator to deliversaid therapeutic pulses to the patient's heart.
 5. The externaldefibrillator of claim 3 wherein said first electrode is coupled to saidpulse generator to deliver said therapeutic pulses to the patient'sheart.
 6. The external defibrillator of claim 3 further comprising asensor circuit coupled to said first electrode to sense intrinsiccardiac signals, said sensor circuit being adapted to transmit saidintrinsic cardiac signals to said detector circuit.
 7. The externaldefibrillator of claim 3 further comprising a self-test and diagnosticcircuit adapted to run tests on said external defibrillator to determineif said external defibrillator is operational.
 8. The externaldefibrillator of claim 3 wherein said detector circuit is adapted todetect intrinsic cardiac signals and said controller is adapted toautomatically generate said command in synchronism with said intrinsiccardiac signals.
 9. The external defibrillator of claim 8 wherein saiddetector circuit is adapted to detect R-waves and said controller isadapted to generate said command at a predetermined interval after saidR-waves.
 10. The external defibrillator of claim 9 wherein saidcontroller is adapted to delay said command after said R-wave, saiddelay being selected to insure that said therapeutic pulses do notcoincide with a T-wave.
 11. The external defibrillator of claim 3wherein said detector circuit is adapted to monitor the heartautomatically and continuously after said electrode is attached to saidpatient.
 12. The external defibrillator of claim 3 further comprising aninhibit switch which may be operated by the patient or an attendant, andwherein said controller is adapted to delay said command if said inhibitswitch has been activated to protect said patient from undesirabletherapeutic pulses.
 13. The external defibrillator of claim 3 furthercomprising a communication module, said controller being adapted to senda message automatically to a remote location through said communicationmodule when said life threatening condition is detected, said messageindicating one of the occurrence and detection of said condition and thepatient's location.
 14. The external defibrillator of claim 3 furthercomprising a data logging memory for logging information descriptive ofsaid life threatening condition and the therapy delivered to revert saidlife threatening condition.
 15. The external defibrillator of claim 3further comprising a display, wherein said controller is adapted toprovide on said display at least one of an instruction for the operationof the defibrillator and information indicative of a condition of thepatient.
 16. The external defibrillator of claim 3 wherein saidcontroller is adapted to define a fully automatic mode of operation,where the device automatically detect life threatening arrhythmias andadministrate therapy.
 17. The external defibrillator of claim 16 whereinsaid fully automatic operation includes an advisory, or semi-automatic,mode of operation, where the device automatically detect lifethreatening arrhythmias and prompt the operator to deliver the therapy.18. The external defibrillator of claim 17 wherein said controllerdefines a manual mode of operation, where the operator has the fullcontrol in delivering therapy.
 19. The external defibrillator of claim16 wherein said controller defines a manual mode of operation, where theoperator has the full control in delivering therapy.
 20. A method ofproviding public cardiac therapy to a patient suffering from a lifethreatening cardiac condition using an external defibrillator having anelectrode, said method comprising the steps of: attaching said electrodeto the patient to sense a physiological signal indicative of intrinsiccardiac signals; detecting a life threatening condition based on saidphysiological condition automatically using a set of generic criteria;and applying automatically therapeutic pulses in response to said lifethreatening condition to said patient; wherein said step of detectingsaid life threatening cardiac condition includes detecting an intrinsicQRS complex and generating an R—R interval based on successive QRScomplexes, and wherein said step of detecting and said step of applyingtherapeutic pulses are performed without any involvement from an outsideattendant.
 21. A method of providing public cardiac therapy to a patientsuffering from a life threatening cardiac condition using an externaldefibrillator having an electrode, said method comprising the steps of:attaching said electrode to the patient to sense a physiological signalindicative of intrinsic cardiac signals; performing a self-test on saidexternal defibrillator after said electrode is attached to said patientto determine if said external defibrillator is operational; detecting alife threatening condition based on said physiological conditionautomatically using a set of generic criteria; and applyingautomatically therapeutic pulses in response to said life threateningcondition to said patient; wherein said step of detecting said lifethreatening cardiac condition and said step of applying therapeuticpulses are performed without any involvement from an outside attendant.22. A method of providing public cardiac therapy to a patient sufferingfrom a life threatening cardiac condition using an externaldefibrillator having an electrode, said method comprising the steps of:attaching said electrode to the patient to sense a physiological signalindicative of intrinsic cardiac signals; detecting a life threateningcardiac condition based on said physiological condition automaticallyusing a set of generic criteria; applying automatically therapeuticpulses in response to said life threatening condition to said patient;said step of detecting said life threatening cardiac condition and saidstep of applying therapeutic pulses are performed without anyinvolvement from an outside attendant; and further applying data loggingeach episode of cardiac condition and the corresponding therapy.
 23. Amethod of providing public cardiac therapy to a patient suffering from alife threatening cardiac condition using an external defibrillatorhaving an electrode, said method comprising the steps of: attaching saidelectrode to the patient to sense a physiological signal indicative ofintrinsic cardiac signals; detecting a life threatening cardiaccondition based on said physiological condition automatically using aset of generic criteria; and applying automatically therapeutic pulsesin response to said life threatening condition to said patient; saidstep of detecting said life threatening cardiac condition and said stepof applying therapeutic pulses are performed without any involvementfrom an outside attendant; wherein said defibrillator includes acommunication module, further comprising generating a message to aremote location indicative of the condition of the patient and sendingsaid message to said remote location using said communication module.24. A method of providing public cardiac therapy to a patient sufferingfrom a life threatening cardiac condition using an externaldefibrillator having an electrode, said method comprising the steps of:attaching said electrode to the patient to sense a physiological signalindicative of intrinsic cardiac signals; detecting a life threateningcardiac condition based on said physiological condition automaticallyusing a set of generic criteria; and applying automatically therapeuticpulses in response to said life threatening condition to said patient;said step of detecting said life threatening cardiac condition and saidstep of applying therapeutic pulses are performed without anyinvolvement from an outside attendant; wherein said externaldefibrillator includes a display, further comprising providing on saiddisplay instructions for the operation of the defibrillator.